When the portal appeared in front of them, the White Demon Rat Leader shouted for the rest to enter the magical gate. She also stayed behind to ensure that each and every of her survivors entered the portal and that was enough for Jin to see the difference between her White Demon Rats compared to the Black ones.
In terms of battle experience, Jin and his minions did not fight against the Demon Rats for long despite the months of longstanding skirmishes, the Dungeon Supplier had received reports that quite a lot of higher ranking Demon Rats would always be the ones to save their skins. So to see the White Demon Rat Leader doing the opposite, it could mean that they were able to listen to reason and perhaps negotiation between the rats might be a possibility.
